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-rw-r--r--sysdeps/x86_64/fpu/e_log2l.S8
-rw-r--r--sysdeps/x86_64/fpu/libm-test-ulps22
2 files changed, 29 insertions, 1 deletions
diff --git a/sysdeps/x86_64/fpu/e_log2l.S b/sysdeps/x86_64/fpu/e_log2l.S
index 956489fc3e..c12906d456 100644
--- a/sysdeps/x86_64/fpu/e_log2l.S
+++ b/sysdeps/x86_64/fpu/e_log2l.S
@@ -45,7 +45,13 @@ ENTRY(__ieee754_log2l)
fnstsw // x-1 : x : 1
andb $0x45, %ah
jz 2f
- fstp %st(1) // x-1 : 1
+ fxam
+ fnstsw
+ andb $0x45, %ah
+ cmpb $0x40, %ah
+ jne 5f
+ fabs // log2(1) is +0 in all rounding modes.
+5: fstp %st(1) // x-1 : 1
fyl2xp1 // log(x)
ret
diff --git a/sysdeps/x86_64/fpu/libm-test-ulps b/sysdeps/x86_64/fpu/libm-test-ulps
index bb549d2b0d..92fef5a134 100644
--- a/sysdeps/x86_64/fpu/libm-test-ulps
+++ b/sysdeps/x86_64/fpu/libm-test-ulps
@@ -1665,6 +1665,28 @@ ifloat: 1
ildouble: 1
ldouble: 1
+Function: "log2_downward":
+double: 2
+float: 2
+idouble: 2
+ifloat: 2
+
+Function: "log2_towardzero":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 1
+ldouble: 1
+
+Function: "log2_upward":
+double: 2
+float: 2
+idouble: 2
+ifloat: 2
+ildouble: 1
+ldouble: 1
+
Function: "log_downward":
float: 1
ifloat: 1